JP6863298B2 - Structure - Google Patents

Description

The present invention relates to a structure composed of a reinforcing fiber, a first resin, and a second resin exhibiting rubber elasticity at room temperature.

In recent years, the market demand for improving rigidity and lightness of industrial products such as automobiles and sports products has been increasing year by year. In order to meet such demands, fiber reinforced resins having excellent rigidity and light weight are widely used in various industrial applications. In these applications, the main focus was on developing products suitable for high-strength, high-rigidity members that utilize the excellent mechanical properties of reinforcing fibers. On the other hand, in fiber reinforced plastics, the development of applications has progressed rapidly in recent years, and applications that require flexibility in addition to strength and rigidity are attracting attention. However, the development of applications utilizing such flexibility has been limited to some applications such as a material in which a rubber polymer is impregnated with heat-resistant fibers as an auxiliary material for molding (Patent Documents). See 1 and 2).

Japanese Unexamined Patent Publication No. 09-277295 Japanese Patent No. 4440963

However, although elasticity and elastic recovery force (cushion property) with respect to load are required for automobile interior materials and medical applications, the methods described in Patent Documents 1 and 2 described above satisfy the elastic recovery force (cushion property). However, there is a problem that it is not possible to obtain a material having a light weight at the same time.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a structure having excellent compressive properties or tensile elongation at break and light weight, which is an index of flexibility.

The present invention for solving the above problems is as follows.
(1) A structure containing a reinforcing fiber, a first resin, and a second resin exhibiting rubber elasticity at room temperature.
The reinforcing fiber is a discontinuous fiber,
A structure formed by coating the intersections between the reinforcing fibers in contact with the first resin and / or the second resin.

According to the structure according to the present invention, it is possible to provide a structure having excellent compressive properties or tensile elongation at break and light weight.

Hereinafter, the structure of the present invention will be described.
The structure of the present invention is a structure containing reinforcing fibers, a first resin, and a second resin exhibiting rubber elasticity at room temperature. The reinforcing fibers are discontinuous fibers and are in contact with each other. It is a structure in which the intersection is covered with the first resin and / or the second resin. Such a present invention has features such as appropriate compression characteristics, tensile elongation at break, light weight, and excellent handleability.

[Reinforcing fiber]
The structure of the present invention has reinforcing fibers. And this reinforcing fiber is a discontinuous fiber. Further, the discontinuous fibers are preferably substantially monofilament-like and randomly dispersed in the structure. By using the reinforcing fibers as discontinuous fibers, it becomes easy to mold the structure precursor or structure of the sheet-like structure into a complicated shape when an external force is applied to form the structure precursor or the structure. Further, by dispersing the reinforcing fibers in a substantially monofilament shape and randomly, the number of reinforcing fibers existing as fiber bundles in the structure is reduced, so that the weak portion at the fiber bundle end of the reinforcing fibers can be minimized, which is excellent. In addition to reinforcement efficiency and reliability, isotropic is also imparted.

Here, the substantially monofilament form means that the reinforcing fiber single yarn is present in the fineness strands of less than 500 threads. More preferably, it is dispersed in a monofilament form. Further, the monofilament form means that it exists as a single yarn. More preferably, the monofilament-like single fibers are randomly dispersed.

The reinforcing fibers in the present invention preferably take a non-woven fabric-like form from the viewpoint of ease of impregnating the reinforcing fibers with the first resin and the second resin. Further, since the reinforcing fiber has a non-woven fabric-like form, in addition to the ease of handling of the non-woven fabric itself, the thermoplastic resin generally having a high viscosity is used as the first resin and / or the second resin. Even when it is used as a resin, it is preferable because it can be easily impregnated. Here, the non-woven fabric-like form refers to a form in which strands and / or monofilaments of reinforcing fibers are dispersed in a plane without regularity, such as chopped strand mat, continuance strand mat, papermaking mat, carding mat, and airlaid mat. (Hereinafter, these are collectively referred to as a reinforcing fiber mat).

It is preferable that the reinforcing fibers in the structure have a mass average fiber length of 1 to 15 mm because the efficiency of reinforcing the reinforcing fibers to the structure can be increased and excellent mechanical properties can be given to the structure. If the mass average fiber length of the reinforcing fibers is less than 1 mm, voids in the structure cannot be efficiently formed, so that the density may increase. In other words, a structure having the same mass but a desired thickness. It is not preferable because it becomes difficult to obtain. On the other hand, when the mass average fiber length of the reinforcing fibers is longer than 15 mm, the reinforcing fibers tend to bend in the structure due to their own weight, which is a factor that hinders the development of mechanical properties, which is not preferable.

For the mass average fiber length, the resin component in the structure was removed by burning or elution, 400 fibers were randomly selected from the remaining reinforcing fibers, and the length was measured up to 10 μm, and the length was measured by the following formula. The mass average fiber length can be obtained.
Mass average fiber length = Σ (Li x Wi / 100)
Li: Measured fiber length (i = 1, 2, 3, ..., N)
Wi: Mass fraction of fiber with fiber length Li (i = 1, 2, 3, ..., N)

The type of reinforcing fiber should be at least one selected from the group consisting of PAN-based carbon fiber, pitch-based carbon fiber, glass fiber, and aramid fiber, in terms of the balance between mechanical properties and lightness when formed into a structure. It is preferable from the viewpoint. Further, the reinforcing fiber may be one that has been surface-treated. The surface treatment includes a treatment with a coupling agent, a treatment with a sizing agent, a treatment with a binding agent, a treatment with an additive, and the like, in addition to the treatment with a metal as a conductor. Further, one type of these reinforcing fibers may be used alone, or two or more types may be used in combination. Among them, PAN-based, pitch-based, rayon-based and other carbon fibers having excellent specific strength and specific rigidity are preferably used from the viewpoint of weight reduction effect. Further, from the viewpoint of enhancing the economic efficiency of the obtained structure, glass fiber is preferably used, and in particular, carbon fiber and glass fiber are preferably used in combination from the viewpoint of the balance between mechanical properties and economic efficiency. Further, from the viewpoint of enhancing the shock absorption and shapeability of the obtained structure, aramid fibers are preferably used, and in particular, carbon fibers and aramid fibers are preferably used in combination from the viewpoint of the balance between mechanical properties and shock absorption. .. Further, from the viewpoint of increasing the conductivity of the obtained structure, reinforcing fibers coated with a metal such as nickel, copper or ytterbium can also be used. Among these, PAN-based carbon fibers having excellent mechanical properties such as strength and elastic modulus can be more preferably used.

It is preferable that the tensile elongation at break of the reinforcing fiber is in the range of 1% or more and 10% or less because the tensile elongation at break of the structure can be 1% or more when the structure is formed. When the tensile elongation at break of the reinforcing fiber is 1% or more, the rubber elasticity of the second resin can be utilized when the structure is formed, and the ductile structure can be formed, which is preferable. On the other hand, when the tensile elongation at break of the structure is 10% or less, it is possible to prevent the structure itself from becoming too flexible, and it is preferable because it is excellent in handleability.

The tensile elongation at break of the reinforcing fiber can be determined by JIS R7606 (2000), and in the measurement of the tensile elongation at break, when the reinforcing fiber is composed of a fiber bundle in which a plurality of single fibers are bundled, the reinforcing fiber is used. It can be obtained by extracting one fiber (single fiber) and subjecting it to measurement.

[First resin]
The structure of the present invention contains a first resin. Here, the first resin in the present invention is a resin other than the second resin described later, that is, a resin that does not exhibit rubber elasticity at room temperature. Examples of such a first resin include thermoplastic resins and thermosetting resins other than the second resin. Further, in the present invention, the thermosetting resin and the thermoplastic resin may be blended.

The first resin has an effect of improving the handleability when composited with the second resin by sealing the reinforcing fibers which are discontinuous fibers. Furthermore, it may have the effect of increasing the affinity between the second resin and the reinforcing fiber.

The first resin preferably has a softening point or a melting point of 50 ° C. or higher. Since the first resin has a softening point or melting point of 50 ° C. or higher, the impregnation temperature when the reinforcing fiber to which the first resin is applied is impregnated with the second resin and the molding when molding the structure. Since the first resin does not melt or disappear at temperature, when the second resin exhibits a crosslinking reaction or a vulcanization reaction, the reaction is not hindered. On the other hand, when the second resin is a thermoplastic resin, it is possible to reduce the melting and disappearance of the first resin at the impregnation temperature.

The first resin is 5 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the reinforcing fibers from the viewpoint of improving the handleability of the reinforcing fibers and improving the affinity between the second resin and the reinforcing fibers. The content is preferably as follows. If the content of the first resin with respect to 100 parts by mass of the reinforcing fiber is less than 5 parts by mass, the handleability of the reinforcing fiber is poor, and if it exceeds 25 parts by mass, the reinforcing fiber is impregnated with the second resin. It may be difficult to obtain a structure because it obstructs the invasion route of the resin of 2. The first resin may be water-soluble or an emulsion from the viewpoint of industrially facilitating the application to the reinforcing fibers.

[Second resin]
The structure of the present invention contains a second resin. Here, the second resin in the present invention is a resin that exhibits rubber elasticity at room temperature. The fact that a resin exhibits rubber elasticity at room temperature means that the resin is deformed at room temperature, the stress required for the deformation is released, and then the resin returns to its original shape. Specifically, after stretching the No. 1 dumbbell test piece described in JIS K6400 (2012), the stress held in the stretching is released. After that, it means that it elastically recovers to almost the original length. However, it is not necessary to completely recover to the original length, and when the dimension before stretching is 100%, the dimensional change after releasing the stress held in the stretching is 80% or more and 120% or less, preferably 120% or less. It may indicate 90% or more and 150% or less. The room temperature means 25 ° C.

The second resin is a group consisting of silicone rubber, ethylene propylene rubber, acrylonitrile butadiene rubber, chloroprene rubber, fluororubber, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer. It is preferable to contain at least one selected from the above. By using the second resin, the cushioning property when the structure is compressed is excellent. Further, from the viewpoint of ease of production, the thermosetting resin is preferably in a liquid state before the crosslinking or vulcanization reaction. From this point of view, silicone rubber and fluororubber can be preferably used. Further, when the second resin is a thermoplastic resin, it is preferable from the viewpoint of producing a structure that it has a melting temperature or a softening temperature and can form a film. From this point of view, polyester-based thermoplastic elastomers are preferable and can be exemplified.

Further, as long as the object of the present invention is not impaired, the first resin and the second resin in the structure according to the present invention are impact resistance improvers such as elastomers or rubber components, and other fillers and additives. May be contained. Examples of fillers and additives include inorganic fillers, flame retardants, conductivity-imparting agents, crystal nucleating agents, UV absorbers, antioxidants, anti-vibration agents, antibacterial agents, insect repellents, deodorants, and anti-coloring agents. , Heat stabilizers, mold release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, antifoaming agents, or coupling agents can be exemplified.

In the structure of the present invention, it is preferable that the intersections between the reinforcing fibers in contact (the intersections between the reinforcing fibers are hereinafter referred to as intersections) are covered with the first resin and / or the second resin.

Further, it is preferable that the coating thickness of the first resin and / or the second resin at the intersection of the reinforcing fibers and / or the reinforcing fibers is within the range of 1 μm or more and 15 μm or less from the viewpoint of expressing the elastic recovery force at the time of compression. The coating state of the intersections coated with the first resin and / or the second resin is at least among the single fibers of the reinforcing fibers constituting the structure from the viewpoint of the shape stability of the structure and the development of compression characteristics. It is sufficient if the intersecting points are covered, but in a more preferable embodiment, the first resin and / or the second resin is in a state of being covered with the above-mentioned thickness around the intersections. Is preferable. In this state, the surface of the intersection between the reinforcing fibers is not exposed by the first resin and / or the second resin, in other words, the reinforcing fibers are wire-shaped by the first resin and / or the second resin. It means that a film is formed. As a result, the structure further has shape stability and sufficient expression of mechanical properties. Further, the coating state of the intersections coated with the first resin and / or the second resin does not have to be coated with all of the reinforcing fibers, and the shape stability of the structure according to the present invention and compression It suffices as long as it does not impair the elastic modulus, and it is preferable that 50% or more of the intersections formed between the reinforcing fibers in contact are covered, and more preferably, the elastic recovery force at the time of compression is exhibited. From the viewpoint, it is 80% or more.

Here, the resin that coats the intersection of the reinforcing fibers and the reinforcing fibers may be either the first resin or the second resin, or may be coated with both the first resin and the second resin. Good. Preferably, the reinforcing fibers are coated with the first resin and then further coated with the second resin, so that the handleability of the reinforcing fibers and the elastic recovery force at the time of compression when the structure is formed are effective. It is preferable from the viewpoint of expression.

Such a covering state can be measured by cutting the structure into small pieces and using a device such as a scanning electron microscope (SEM) that can observe the cross section at a high magnification. For example, the first resin and / or the first resin covering the intersections between the reinforcing fibers from any 50 places where the cross section of the reinforcing fibers was cut in the image obtained by observing and photographing at a magnification of 3000 times by SEM. The coating thickness of the second resin can be measured. As a representative value of the thickness of the first resin and / or the second resin covering the intersection, it can be obtained by using the arithmetic average value of the measurement results at these 50 points. At the time of measurement, the reinforcing fibers to which the second resin is not applied in advance (the intersections of the reinforcing fibers bonded by the first resin as described above) are observed and photographed in the same manner as above, and the diameter of the intersection is determined. By subtracting the diameter of the above-mentioned intersection from the diameter of the intersection obtained from the image obtained after applying the second resin, a more accurate measurement result can be obtained. For the diameter of such an intersection, the maximum diameter of the cross section of the intersection obtained from the observation field of view is obtained. The fiber diameter in the direction perpendicular to the obtained maximum diameter is measured, and the arithmetic mean is taken as the diameter of the intersection and the diameter of the intersection covered with the first resin and / or the second resin.

The coating ratio can be measured by cutting the structure into small pieces and using a device such as a scanning electron microscope (SEM) that can observe the cross section at a high magnification. For example, the number of intersections covered with the first resin and / or the second resin was measured from any 400 points obtained from the obtained image by observing and photographing at a magnification of 1000 times by SEM. By dividing by the number of (that is, 400), the coating ratio in which the intersections are covered with the first resin and / or the second resin can be calculated. Although it is possible to obtain the coating ratio at less than 400 places, it is preferable to set the number at 400 places or more because the error between the measurers can be reduced.

The second resin preferably has a tensile elongation at break of 200% or more and a tensile strength at break of 10 MPa or more because the elongation at break of the structure can be 1% or more. On the other hand, when the tensile elongation at break of the second resin is 200% or more, the elongation at break of the second resin is sufficient, so that it is possible to prevent the structure from becoming brittle. it can. The tensile elongation at break of the second resin is more preferably 500% or more. On the other hand, by setting the tensile breaking strength of the second resin to 10 MPa or more, the elastic recovery force at the time of desired compression in the structure can be made sufficient. The tensile breaking strength of the second resin is more preferably 25 MPa or more.
The tensile elongation at break and the tensile strength at break of the second resin can be determined by a tensile test (JIS K6400 (2012)).

〔Structure〕
The structure in the present invention preferably has voids, and the density is preferably 0.01 g / cm ³ or more and 1.3 g / cm ³ or less. When the density ρ of the structure is 1.3 g / cm ³ or less, it is possible to prevent an increase in mass when the structure is formed and to ensure lightness, which is preferable. Since the density of the structure is 0.01 g / cm ³ or more, the density of the structure itself is excellent, and the volume ratio of the reinforcing fibers and the resin components (first resin and second resin) in the structure is high. It is possible to prevent it from becoming too small. Therefore, it is preferable that the structure has a well-balanced elastic resilience and tensile strength. From the above viewpoint, the density of the structure ^{is preferably 0.03 g / cm 3} or more, and the weight is lighter. Considering the balance between elastic resilience and tensile strength, 0.1 g / cm ³ or more is preferable.

Assuming that the structure of the present invention is 100% by volume, the volume content of the voids is preferably in the range of 10% by volume or more and 97% by volume or less. When the volume content of the voids is 10% by volume or more, it is preferable because the lightness of the structure is satisfied. On the other hand, when the volume content of the voids is 97% by volume or less, in other words, the thickness of the resin components (first resin and second resin) coated around the reinforcing fibers is sufficiently secured. Since the reinforcing fibers are sufficiently reinforced in the structure, the mechanical properties can be improved, which is preferable.

Here, the void refers to a space formed by the reinforcing fibers coated with the resin components (the first resin and the second resin) forming a columnar support, which are overlapped or intersected with each other. .. For example, when a structure precursor obtained by preliminarily impregnating a reinforcing fiber with a resin component (first resin and second resin) is heated to obtain a structure, the resin component (first resin and second resin) associated with the heating is heated. By melting or softening the resin), the reinforcing fibers are raised to form voids. This is based on the property that in the structure precursor, the internal reinforcing fibers that have been compressed by pressurization are raised by the raising force derived from the elastic modulus.

In the present invention, the volume content of the resin (total of the first resin and the second resin), the reinforcing fibers, and the voids constituting the structure is 100% by volume.
That is, when the total of the resin (total of the first resin and the second resin), the reinforcing fibers, and the voids is 100% by volume, the resin in the structure (the total of the first resin and the second resin) The volume content is preferably in the range of 2.5% by volume or more and 85% by volume or less. When the volume content of the resin (total of the first resin and the second resin) is 2.5% by volume or more, the reinforcing fibers in the structure are bound to each other, and the reinforcing effect of the reinforcing fibers is sufficient. Therefore, it is preferable because the mechanical properties of the structure, particularly the bending properties, can be satisfied. On the other hand, when the volume content of the resin (total of the first resin and the second resin) is 85% by volume or less, the amount of the resin is small and it becomes easy to form a void structure, which is preferable.

Further, the structure of the present invention preferably has an elastic recovery force of 1 MPa or more when compressed at 50%. Here, the elastic recovery force is the compression strength when the structure measured by JIS K7220 (2006) is compressed by 50% in the thickness direction. Since the elastic recovery force at 50% compression in the thickness direction is 1 MPa or more, the structure is excellent in shape retention, and therefore, for example, it is excellent in handleability when attached to another member as a product. Further, in practice, when the in-plane direction of the structure is used as the direction in which the load is applied, the structure can withstand a slight load and is deformed when a load exceeding a certain level is applied. When used as a product, it is preferable from the viewpoint of protection to workers at the time of installation. If the elastic recovery force at the time of 50% compression is 1 MPa or more, there is no problem in practical use, but it is preferably 3 MPa or more.

Further, the structure preferably has a tensile elongation at break of 1% or more and 20% or less. Here, the tensile elongation at break is the elongation at break observed in the tensile test in the fiber orientation direction of the structure measured by JIS K6400 (2012). The fiber orientation direction means the length direction of the reinforcing fibers. When the tensile elongation at break is 1% or more and 20% or less, bending and twisting are reduced when handling the structure, and the handleability is excellent. The tensile elongation at break of the structure is preferably 3% or more and 15% or less, more preferably 5% or more and 15% or less from the viewpoint of handleability.

The method for producing a structure according to the present invention can be produced via a first structure precursor in which a mat-like reinforcing fiber (hereinafter, simply referred to as a reinforcing fiber mat) is impregnated with a first resin in advance. it can. As a method for producing the first structure precursor, a reinforcing fiber mat and a first resin are laminated, and pressure is applied in a state where the first resin is melted or heated to a temperature equal to or higher than the softening temperature of the first resin. However, it is preferable to use a method of impregnating the reinforcing fiber mat with the first resin from the viewpoint of ease of production. On the other hand, when the first resin is in the form of an aqueous solution or an emulsion, a method of adding the first resin to the reinforcing fiber mat by a method such as curtain coating, dipping, or dipping to dry the water or solvent can also be adopted. However, any method can be adopted as long as it can apply the first resin to the reinforcing fiber mat.

Further, the structure can be produced via a second structure precursor in which the first structure precursor is impregnated with the second resin. The method of applying the second resin to the first structure precursor can be carried out by further impregnating the first structure precursor with the second resin. For example, when the second resin exhibits thermoplasticity, the first structure precursor and the second resin are laminated, and the second resin is melted or heated to a temperature higher than the softening temperature of the second resin. It is preferable to use a method of applying pressure in the state and impregnating the reinforcing fiber mat of the first structure precursor from the viewpoint of ease of production. Specifically, a method of heating and pressurizing a laminate in which the second resin is arranged from both sides in the thickness direction of the first structure precursor to melt and impregnate the first structure precursor can be preferably exemplified. As the equipment for realizing each of the above methods, a compression molding machine or a double belt press can be preferably used. In the case of the batch type, it is the former, and productivity can be improved by using an intermittent press system in which two or more machines for heating and cooling are arranged in parallel. In the case of the continuous type, it is the latter, and continuous processing can be easily performed, so that continuous productivity is excellent.

When the second resin is dispersed in a solvent or shows a liquid state at room temperature, the first structure precursor may be coated with a curtain coat, dip, immersed, or vacuum pressure molded. A method in which the second resin is infiltrated to dry the water and solvent, or the first structure precursor in which the second resin is infiltrated is brought to a temperature at which the second resin starts a cross-linking reaction or a vulcanization reaction. The structure can be obtained by heating.

The structure of the present invention can be used as a component for automobile interior / exterior, electrical / electronic equipment housing, bicycle, sports equipment structural material, aircraft interior material, medical equipment, etc. from the viewpoint of elastic recovery force and light weight during compression. It is preferably used. Among them, it is particularly suitable for a module member composed of a plurality of parts.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(1) Volume content of voids in the structure A test piece is cut out from the structure to a length of 10 mm and a width of 10 mm, and the cross section is observed with a scanning electron microscope (SEM) (S-4800 type manufactured by Hitachi High-Technologies Corporation). , 10 places were photographed at equal intervals from the surface of the structure at a magnification of 1000 times. For each image to determine the area A _a void in the image. Moreover, to calculate the porosity by dividing the area A _a void in the area of the entire image. The volume content of the voids in the structure was determined by an arithmetic mean from the void ratios of a total of 50 locations taken at 10 locations each with 5 test pieces.

(2) Density of the structure A test piece was cut out from the structure, and the apparent density of the structure was measured with reference to JIS K7222 (2005). The dimensions of the test piece were 100 mm in length and 100 mm in width. The length, width, and thickness of the test piece were measured with a micrometer, and the volume V of the test piece was calculated from the obtained values. Moreover, the mass M of the cut-out test piece was measured with an electronic balance. The density ρ of the structure was calculated by substituting the obtained mass M and volume V into the following equation.
ρ [g / cm ³ ] = 10 ³ x M [g] / V [mm ³ ]

(3) Elastic recovery force at 50% compression of the structure A test piece was cut out from the structure, and the compression characteristics of the structure were measured with reference to JIS K7220 (2006). The test piece was cut out to a length of 25 ± 1 mm and a width of 25 ± 1 mm. The compression characteristics of the obtained test piece were measured using a universal testing machine. _{At this time, the compressive strength σ m} was calculated from the following equation using _{the maximum force F m} reached when the deformation rate was 50% and the bottom cross-sectional area A ₀ of the test piece before the test, and used as the elastic recovery force. As a measuring device, an "Instron (registered trademark)" 5565 type universal material testing machine (manufactured by Instron Japan Co., Ltd.) was used.
σ _m [MPa] = F _m [N] / A ₀ [mm ² ]

(4) Tensile elongation at break of the structure A test piece was cut out from the structure, and the tensile characteristics of the structure were measured with reference to JIS K6400 (2012). The test piece was cut into No. 1 form. The tensile properties of the obtained test piece were measured using a universal testing machine. As a measuring device, an "Instron (registered trademark)" 5565 type universal material testing machine (manufactured by Instron Japan Co., Ltd.) was used.

(5) Resin coating thickness in the structure A test piece was cut out to a length of 10 mm and a width of 10 mm, and the cross section was observed with a scanning electron microscope (SEM) (S-4800 type manufactured by Hitachi High-Technologies Corporation). Arbitrary 10 points were photographed at a magnification of 3000 times. The coating thickness of the resin covering the intersections of the reinforcing fibers was measured from any 50 points where the cross section of the intersections of the reinforcing fibers of the obtained image was cut, and the arithmetic mean of the 50 points was taken as the coating thickness of the resin. did.

(6) Content of First Resin with respect to Reinforcing Fiber The reinforcing fiber before coating the first resin was cut into a length of 25 ± 1 mm and a width of 25 ± 1 mm, and the mass W1 was measured. Then, the mass W2 of the reinforcing fiber containing the first resin was measured. The content Wr of the first resin was calculated by the following formula, and the amount per 100 parts by mass of the reinforcing fiber was calculated.
Content of the first resin with respect to the reinforcing fiber Wr (mass) = W2-W1

(7) Softening point or melting point of the first resin The melting point was evaluated by a differential scanning calorimeter (DSC). A 5 mg sample was packed in a closed sample container, and the temperature was raised from 30 ° C. to 300 ° C. at a heating rate of 10 ° C./min for evaluation. A Pyrisl DSC manufactured by PerkinElmer was used as the evaluation device.
For those for which it is difficult to evaluate the melting point (when the melting point does not exist), the Vicat softening temperature was evaluated in accordance with ISO306 (2004) (using a weight of 10N) and used as a softening point.

(8) Tensile Properties of Second Resin A tensile test was conducted with reference to the method described in JIS K6400 (2012), and tensile elongation at break and tensile strength at break were evaluated. The tensile properties of the obtained test piece were measured using a universal testing machine. As a measuring device, an "Instron (registered trademark)" 5565 type universal material testing machine (manufactured by Instron Japan Co., Ltd.) was used.
Regarding the presence or absence of rubber elasticity of the second resin, in the same test, the stress is released at the time of 200% elongation (using the length of the test piece as the standard 100%), and it is visually observed whether the shape returns to 150% or less. Confirmed at. When it returns to 150% or less, it is evaluated as "Yes", and when it exceeds 150% or it breaks, it is evaluated as "No".
As the test piece, a No. 1 dumbbell test piece shape was prepared and used for the test. As for the preparation of the test piece, the test piece was prepared by injection molding for the second resin exhibiting thermoplasticity. Regarding the second resin, which exhibits liquid properties at room temperature, the second resin is poured into a mold having a recess having the same shape as the No. 1 dumbbell test piece, the mold is closed, and then cross-linking or curing is performed. A test piece was prepared by curing at a temperature / time of

(9) Volume content of reinforcing fibers in the structure Vf
After measuring the mass Ws of the structure, the structure was heated in air at 500 ° C. for 30 minutes to burn off the resin component, and the mass Wf of the remaining reinforcing fibers was measured and calculated by the following formula. At this time, the densities of the reinforcing fibers and the resin are measured according to the in-liquid weighing method of JIS Z8807 (2012).
Vf (volume%) = (Wf / ρf) / {Wf / ρf + (Ws-Wf) / ρr} × 100
ρf: Density of reinforcing fibers (g / cm ³ )
ρr: Resin density (g / cm ³ )

(10) Volume Content of First Resin A precursor of a structure composed of only reinforcing fibers and the first resin was prepared, and the volume content of voids in the precursor obtained by the same method as in (1) was reinforced. Using the value of the volume content of the fiber, the volume content of the first resin was determined by the following formula.
Vr1 (volume%) of the first resin = 100- (Vf + Va)
Vf: Volume fraction of reinforcing fiber (volume%)
Va: Volume fraction of voids (volume%)
Vr1: Volume fraction of the first resin (volume%)

(11) Volume content of the second resin The volume content of the voids in the structure obtained from (1), (9), and (10), the volume content of the reinforcing fibers, and the volume content of the first resin. Using the value of, the volume content of the resin was determined by the following formula.
Vr2 (volume%) of the second resin = 100- (Vf + Va + Vr1)
Vf: Volume fraction of reinforcing fiber (volume%)
Va: Volume fraction of voids (volume%)
Vr1: Volume fraction of the first resin (volume%)

(12) Resin coating ratio in the structure A test piece was cut out to a length of 10 mm and a width of 10 mm, and the cross section was observed with a scanning electron microscope (SEM) (S-4800 type manufactured by Hitachi High-Technologies Corporation). Arbitrary 10 points were photographed at a magnification of 1000 times. Regarding the intersections of the reinforcing fibers from the obtained image, the number of the intersections of the reinforcing fibers and the number of the resin-coated points coated on the intersections of the reinforcing fibers were measured from any 40 points, and the resin was coated by the following formula. The ratio (%) was used.
Resin coating ratio (%) = (C2 / C1) x 100
C1: Number of measured intersections (pieces)
C2: Number of intersections covered with resin in C1 (pieces)

The following materials were used in the following examples and comparative examples.
[Carbon fiber]
A copolymer containing polyacrylonitrile as a main component was spun, fired, and surface-oxidized to obtain continuous carbon fibers having a total number of single yarns of 12,000. The characteristics of this continuous carbon fiber were as shown below.
Specific gravity: 1.8
Tensile strength: 4600 MPa
Tensile modulus: 220 GPa
Tensile elongation at break: 2.1%

[Aramid fiber]
Aramid fiber (“Kevlar” (registered trademark) 29 manufactured by Toray DuPont Co., Ltd.) was used.
Specific gravity: 1.44
Tensile strength: 2900 MPa
Tensile modulus: 70 GPa
Tensile fracture elongation: 3.6%

[polyamide]
As the first resin, a water-soluble polyamide resin (Toray Industries, Inc. "AQ Nylon" (registered trademark) P-70) was used.
Softening point: 85 ° C

[Polyurethane]
As the first resin, a polyurethane aqueous dispersion (Daiichi Kogyo Seiyaku Co., Ltd. "Superflex" (registered trademark) 150) was used.
Softening point: 195 ° C
Melting point: 212 ° C

[Polyester resin]
^{A resin film having a basis weight of 121 g / m 2} made of a polyester resin (“Hitrel” (registered trademark) SB754 manufactured by Toray Industries, Inc.) was prepared and used as the second resin. The characteristics of the obtained resin film are shown in Table 1.

[silicone rubber]
Silicone rubber (RBL-9200-40 manufactured by Toray Dow Corning Silicone Co., Ltd.) was used. A silicone rubber is prepared by mixing the A agent (main agent) and the B agent (curing agent) of this silicone rubber at a mixing ratio of 1: 1 and collecting an amount so as to be ^{124 g / m 2 and stirring.} , Used as a second resin. The characteristics of silicone rubber are shown in Table 1.

[Epoxy resin]
Epoxy resin (Japan Epoxy Resin Co., Ltd. "Epicoat" (registered trademark) 828:30 parts by mass, "Epicoat" (registered trademark) 1001:35 parts by mass, "Epicoat" (registered trademark) 154:35 parts by mass) After 5 parts by mass of the thermoplastic resin polyvinylformal (Chisso Co., Ltd. "Vinirec" (registered trademark) K) is heat-kneaded with a kneader to uniformly dissolve the polyvinylformal, the curing agent disiandiamide (Japan Epoxy Resin Co., Ltd. DICY7) ) 3.5 parts by mass and 7 parts by mass of the curing accelerator 4,4-methylenebis (phenyldimethylurea) (PIT I Japan Co., Ltd. "Omicure" (registered trademark) 52) are kneaded with a kneader. An uncured epoxy resin composition was prepared. From this, a resin film having a basis weight of 132 g / m ² was prepared using a knife coater and used as a second resin. The characteristics of the obtained resin film are shown in Table 1.

(Example 1)
Carbon fiber was used as the reinforcing fiber and cut to 6 mm with a cartridge cutter to obtain chopped carbon fiber. A dispersion liquid having a concentration of 0.1% by mass consisting of water and a surfactant (polyoxyethylene lauryl ether (trade name) manufactured by Nakaraitex Co., Ltd.) was prepared, and this dispersion liquid and chopped carbon fiber were used. , Manufactured reinforced fiber mat. The manufacturing apparatus includes a cylindrical container having a diameter of 1000 mm having an opening cock at the bottom of the container as a dispersion tank, and a linear transport portion (inclination angle of 30 °) connecting the dispersion tank and the paper making tank. A stirrer is attached to the opening on the upper surface of the dispersion tank, and chopped carbon fibers and a dispersion liquid (dispersion medium) can be charged through the opening. The papermaking tank is provided with a mesh conveyor having a papermaking surface having a width of 500 mm at the bottom, and a conveyor capable of transporting a carbon fiber base material (papermaking base material) is connected to the mesh conveyor. Papermaking was carried out with the carbon fiber concentration in the dispersion liquid being 0.05% by mass. The paper-made reinforcing fiber mat was dried in a drying oven at 200 ° C. for 30 minutes to obtain a reinforcing fiber mat. The basis weight obtained was 50 g / m ² .

Polyamide as the first resin was dissolved in water so as to be 1% by mass. This polyamide aqueous solution was applied to the reinforcing fiber mat obtained above. It was placed in a hot air oven whose temperature was controlled to 110 ° C. and dried for 2 hours to obtain a first structure precursor. The adhesion rate of the polyamide of the obtained first structure precursor was 10 parts by mass with respect to 100 parts by mass of the reinforcing fiber mat.
A polyester resin is used as the second resin in the first structure precursor, and [second resin / first structure precursor / second resin / first structure precursor / second resin / first 1 structure precursor / 2nd resin / 1st structure precursor / 1st structure precursor / 2nd resin / 1st structure precursor / 2nd resin / 1st structure A laminate was prepared in which the body precursor / second resin / first structure precursor / second resin] was arranged in this order. Then, a structure was obtained by going through the following steps (1) to (5). The characteristics are shown in Table 2.
(1) The laminate is placed in a press molding die cavity preheated to 200 ° C., and the die is closed.
(2) Next, after holding for 120 seconds, a pressure of 3 MPa is applied to hold for another 60 seconds.
(3) After the step (2), the mold cavity is opened, a metal spacer is inserted at the end thereof, and the thickness at the time of obtaining the structure is adjusted to 3.4 mm.
(4) After that, the mold cavity is fastened again, and the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(5) Open the mold and take out the structure.

(Example 2)
A laminate similar to that in Example 1 was obtained except that the content of the first resin was changed to 8 parts by mass, and then a structure was obtained by going through the following steps (1) to (4). The characteristics are shown in Table 2.
(1) The laminate is placed in a press molding die cavity preheated to 200 ° C., and the die is closed.
(2) Next, a pressure of 3 MPa is applied and the mixture is held for another 120 seconds.
(3) After that, the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(4) Open the mold and take out the structure.

(Example 3)
The same as in Example 1 except that the first resin was changed from polyamide to polyurethane, the content of the first resin was changed to 10 parts by mass, and the mass ratio of the reinforcing fibers in the structure was changed to 55% by mass. A laminate was obtained, and then a structure was obtained by going through the following steps (1) to (5). The characteristics are shown in Table 2.
(1) The laminate is placed in a press molding die cavity preheated to 200 ° C., and the die is closed.
(2) Next, after holding for 120 seconds, a pressure of 3 MPa is applied to hold for another 60 seconds.
(3) After the step (2), the mold cavity is opened, a metal spacer is inserted at the end thereof, and the thickness at the time of obtaining the structure is adjusted to 5.9 mm.
(4) After that, the mold cavity is fastened again, and the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(5) Open the mold and take out the structure.

(Example 4)
In Example 4, the second resin was changed from polyester resin to silicone rubber. A stack of eight first structure precursors used in Example 1 is placed in a stainless steel container, silicone rubber is poured into the container, and the first structure precursor is squeezed with a hand roller until the silicone rubber is impregnated. This produced a laminate. Then, a structure was obtained by going through the following steps (1) to (4). The characteristics are shown in Table 2.
(1) The laminate is placed in a press molding die cavity preheated to 150 ° C., and the die is closed.
(2) Next, a pressure of 3 MPa is applied and the mixture is held for another 60 minutes.
(3) After that, the cavity temperature is cooled to 30 ° C. while maintaining the pressure.
(4) Open the mold and take out the structure.

(Example 5)
A laminate was obtained in the same manner as in Example 4. Then, a structure was obtained by going through the following steps (1) to (4). The characteristics are shown in Table 2.
(1) The laminate is placed in a press molding die cavity preheated to 150 ° C.
(2) Next, a metal spacer is inserted into the end of the mold cavity, adjusted so that the thickness when obtaining the structure is 3.3 mm, and the mold is closed and held for 10 minutes.
(3) After that, the cavity temperature is cooled to 30 ° C. while maintaining the pressure.
(4) Open the mold and take out the structure.

(Example 6)
A first structure precursor was obtained in the same manner as in Example 1. A structure was obtained in the same manner as in Example 1 except that the amount of the second resin was adjusted so that the mass ratio of the reinforcing fibers in the structure was 55% by mass to obtain a laminate. The characteristics are shown in Table 2.

(Example 7)
The structure was the same as in Example 1, except that the reinforcing fibers were changed from carbon fibers to aramid fibers, the first resin was changed from polyamide to polyurethane, and the mass ratio of the aramid fibers in the structure was changed to 25% by mass. Obtained. The characteristics are shown in Table 2.

(Example 8)
The reinforcing fiber was changed from carbon fiber to aramid fiber, the first resin was changed from polyamide to polyurethane, the content of the first resin was changed to 10 parts by mass, and the mass ratio of aramid fiber in the structure was changed to 25% by mass. A structure was obtained in the same manner as in Example 2 except that it was replaced. The characteristics are shown in Table 2.

(Comparative Example 1)
A laminate similar to that of Example 1 was obtained except that the content of the first resin was replaced with 8 parts by mass and the second resin was replaced with an epoxy resin, and then the following steps (1) to A structure was obtained by going through (4). The characteristics are shown in Table 3.
(1) The laminate is placed in a press molding die cavity preheated to 150 ° C., and the die is closed.
(2) Next, a pressure of 3 MPa is applied and the mixture is held for another 10 minutes.
(3) After that, the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(4) Open the mold and take out the structure.

(Comparative Example 2)
The first resin was replaced with polyurethane from polyamide, and the content with respect to the reinforcing fibers was adjusted to 30 parts by mass to prepare a laminate. Then, a structure was obtained by going through the following steps (1) to (4). The characteristics are shown in Table 3.
(1) The laminate is placed in a press molding die cavity preheated to 150 ° C.
(2) Next, a metal spacer is inserted into the end of the mold cavity, the thickness when obtaining the structure is adjusted to 1.5 mm, and the mold is closed and held for 10 minutes.
(3) After that, the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(4) Open the mold and take out the structure.

(Comparative Example 3)
A laminate was prepared by replacing the reinforcing fibers with carbon fibers and using aramid fibers and using an epoxy resin as the second resin without using the first resin. Then, a structure was obtained by going through the following steps (1) to (4). The characteristics are shown in Table 3.
(1) The laminate is placed in a press molding die cavity preheated to 150 ° C., and the die is closed.
(2) Next, a pressure of 3 MPa is applied and the mixture is held for another 10 minutes.
(3) After that, the cavity temperature is cooled to 50 ° C. while maintaining the pressure.
(4) Open the mold and take out the structure.

〔Consideration〕
According to Examples 1, 3, 5 to 7, the structure is composed of a reinforcing fiber, a first resin, and a second resin exhibiting rubber elasticity at room temperature, and discontinuous fibers are used as the reinforcing fibers. The structures in which the intersections between the reinforcing fibers bonded with the first resin are coated with the second resin have an elastic recovery force of 1 MPa or more and a tensile elongation of 1% at the time of 50% compression. The above results were obtained. Further, even in Examples 2, 4 and 8 in which the elastic recovery force at the time of 50% compression cannot be measured due to the small porosity, it is found from the comparison with Comparative Examples 1 and 3 that the tensile elongation at break is excellent, which is excellent. It was found that both flexibility and lightness were achieved. Further, in comparison with Examples 1 to 8 and Comparative Example 3, since the reinforcing fibers are coated with the first resin, the mat made of the reinforcing fibers does not come apart during transportation and is excellent in handling. I was able to confirm that. Further, in Comparative Examples 1 and 3, since the second resin was an epoxy resin having no rubber elasticity at room temperature, it did not show the elastic recovery force at the time of 50% compression. Further, in Comparative Example 1, the tensile elongation was 1% or more, but since it was a structure having no voids, it was considered that the tensile elongation of the reinforcing fibers was reflected. Further, according to Examples 3 and 7, a structure having an appropriate tensile elongation at break could be obtained even if the type of the reinforcing fiber was changed. From the above results, it is clear that the structure within the scope of the present invention has excellent compressive and tensile properties.

According to the present invention, it is possible to provide a structure having excellent flexibility and light weight represented by elastic recovery force at the time of compression or tensile elongation at break.

Claims (11)

A structure containing a reinforcing fiber, a first resin, and a second resin exhibiting rubber elasticity at room temperature.
The reinforcing fiber is a discontinuous fiber,
The intersection between the reinforcing fibers in contact, the Ri first name resin and / or coated by the second resin, elastic recovery force at 50% compression of the structure Ru der least 1 MPa, structure body. The structure according to claim 1, wherein the structure has voids and the density of the structure is 0.01 g / cm ³ or more and 1.3 g / cm ³ or less. The structure according to claim 2, wherein the volume content of the voids in the structure is in the range of 10% by volume or more and 97% by volume or less. The structure according to any one of claims 1 to 3 , wherein the structure has a tensile elongation at break of 1% or more and 20% or less. The structure according to any one of claims 1 to 4 , wherein the reinforcing fiber has a tensile elongation at break of 1% or more and 10% or less. The structure according to any one of claims 1 to 5 , wherein the reinforcing fiber contains at least one selected from the group consisting of PAN-based carbon fiber, pitch-based carbon fiber, glass fiber, and aramid fiber. The structure according to any one of claims 1 to 6 , wherein the coating thickness of the first resin and / or the second resin that covers the intersections between the reinforcing fibers is in the range of 1 μm or more and 15 μm or less. The structure according to any one of claims 1 to 7 , wherein the second resin has a tensile elongation at break of 200% or more and a tensile strength at break of 10 MPa or more. The second resin is composed of silicone rubber, ethylene propylene rubber, acrylonitrile butadiene rubber, chloroprene rubber, fluororubber, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer. The structure according to any one of claims 1 to 8 , which comprises at least one selected from the group. The structure according to any one of claims 1 to 9 , wherein the first resin has a softening point or a melting point of 50 ° C. or higher. The first resin relative to the reinforcing fibers to 100 parts by mass, not more than 5 parts by mass or more 25 parts by mass, the structure of any of claims 1 to 1 0.